Two-thirds of acute abdominal aortic aneurysms occurred at ages 75 and up

Action Points

Deaths due to abdominal aortic aneurysm rupture are occurring more frequently in older people, and screening strategies should be updated to reflect this demographic shift.

Note that amost all (96.4%) of the ruptures among men younger than age 75 involved smokers or former smokers, suggesting that screening strategies in younger men should target smokers.

Deaths due to abdominal aortic aneurysm (AAA) rupture are occurring more frequently in older people, and screening strategies should be updated to reflect this demographic shift, U.K. researchers suggested.

Based on population projections and current incidence trends, Dominic P.J. Howard, DPhil, of John Radcliffe Hospital in Oxford, and colleagues estimated the impact of screening strategies in a U.K. population of 92,728 people. Over a 12-year period between 2002 and 2014, 103 acute AAA events occurred in the population, they reported in the Journal of the American Heart Association.

"Incidence/100,000/year was 55 in men ages 65 to 74 years, but increased to 112 at 75 to 85 and 298 at ≥85, with 66.0% of all events occurring at age ≥75 years," they wrote. "Incidence at ages 65 to 74 was highest in male smokers (274), with 96.4% of events in men <75 years occurring in ever-smokers."

When the researchers extrapolated this event rate to the entire population of the U.K., using trial evidence of screening efficacy, they concluded that screening only male smokers at age 65 and average-risk men at age 75 would prevent approximately 20% of AAA deaths, compared to just 5.6% of deaths prevented with the current screening strategy.

Almost all (96.4%) of the ruptures among men younger than age 75 involved smokers or former smokers, suggesting that screening strategies in younger men should target smokers, they stated.

In addition, given that two-thirds of AAA occurred in people who were ages 75 and older, screening older populations should be considered, they said.

"We have calculated that if the national U.K. screening policy was modified to screen only male current smokers age 65 and then all men at age 75, this could result in an almost four-fold increase in the number of deaths prevented and a three-fold increase in the number of life-years saved compared to the current U.K. strategy, with about a 20% reduction in the number of scans required," Howard explained in email to MedPage Today.

Howard's group looked at patients enrolled in the Oxford Vascular Study (OXVASC) that include over 90,000 individuals over a dozen years.

A key goal of the study was to examine the potential impact of a more targeted screening approach on AAA death rates, Howard said.

AAA rupture is associated with an 80% mortality rate, compared with only a 2% to 6% 30-day mortality for elective surgical repair of AAAs detected through screening, the researchers wrote.

Smoking, high blood pressure, male gender, and older age are the four key risk factors for AAA.

Current AAA screening guidelines in the U.S. are similar to those in the U.K., with the U.S. Preventive Services Task Force recommending one-time ultrasound screening between the ages of 65 and 75 for men, but not women.

However, Howard and colleagues found that more than one in four acute AAA events occurred in women. They further estimated that the event rate among women is likely to rise to one in three by 2030.

They suggested that offering screening to women with risk factors and screening all women at 75 with hypertension should be evaluated in randomized trials.

"Our data have implications for national screening strategies for prevention and rupture of AAA," Howard noted. "The current screening programs in the U.K., Europe, and U.S. are a major step forward in treating this condition. However, we hope that our findings may lead to modification of screening programs with subsequent future increases in death prevented from ruptured aortic aneurysms, and greater screening efficacy with reduced costs."

The study had some limitations. More than 90% of the participants in the OXVASC database is white. Also, some sudden deaths from AAA in the community may have gone undiagnosed. "Finally,

projections of future event rates will inevitably be prone to error given the uncertainty about changes in risk factors and preventive treatments in the future," the authors stated.

American Heart Association spokesperson Ann Bolger, MD, of the University of California San Francisco, said the study makes a strong case for revisiting screening strategies for AAA.

"This study shows that a nonsmoker at age 65 is very unlikely to have an abdominal aneurysm, but this is not necessarily true for a 75 or 85 year old without this risk factor," she told MedPage Today. "If we do a better job of stratifying risk -- meaning that we look at the highest risk people early and more average-risk people later on -- we could save lives."

She said the study should be seen as an invitation to think more broadly about screening guidelines.

"This is a really good reminder that screening strategies are based on what we know about demographics, what we know about the time course of an illness, and what we know about the sensitivity of a screening test," she said. "It is important to remember that all of these things are constantly changing."

The Oxford Vascular Study is funded by the Wellcome Trust, Wolfson Foundation, U.K. Medical Research Council, the Dunhill Medical Trust, the Stroke Association, the National Institute for Health Research (NIHR), and the NIHR Biomedical Research Center.

The researchers disclosed no relevant relationships with industry.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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